The drying of garments, bed clothing and linen in general after being washed is a task that can be problematic, mainly in rainy regions or in homes without drying areas.
In view of the above, home dryer machines are additional accessories to washing machines that assist in the duties of cleaning garments.
Generally and basically, the operation of a dryer machine consists in allowing forced hot air to enter into a rotatory drum, inside which wet clothes rotate.
Two main drying systems exist, namely:
Drying by evacuation, wherein wet air is ejected out via a tube, where the tube length should be so that it avoids condensation of water steam before exiting to the outside,
Drying by condensation, wherein wet air is directed to a condenser where it is converted into water and subsequently recollected.
There is a third drying system known as drying by centrifugation, wherein garments are loaded in cylindrical perforated drum, which rotates at high revolutions, thus removing water from said garments.
In the state of the art there are several dryer machines that use different drying methods for drying garments, such as the U.S. Pat. No. 7,942,937 which refers to a control method of a dryer machine that reads a temperature variation per time unit allowing drying according to the quantity and type of objects to be dried. The method comprising the steps of starting a drying procedure; measuring a temperature variation per time unit during the drying procedure; calculating a total drying time based on the temperature variation measured per time unit; and performing the drying procedure for the calculated total drying time. The drying time determines which step is to be repeated if a substantial increment in the temperature variation is sensed.
The U.S. patent application Ser. No. 11/509,798 (Publication No. US 2007/0068036 A1) relates to a laundry cleaning appliance including a drum, a heater, a blower, a dryness sensor and a controller. The drum accommodates garments. The heater and the blower supply hot air to the drum. The dryness sensor senses the dryness of garments. The controller controls the temperature of the heater depending on changes in the dryness of fabric garments sensed by the dryness sensor. The temperature of hot air is controlled so as to be high when the dryness of garments is low, so that there are advantages in that the performance of drying garments is improved, and the drying time of fabrics is shorten. The temperature of hot air is controlled so as to be low when the dryness of garments is high, so that there are advantages in that the over-dry of fabrics is prevented, and therefore damages to garments due to said predetermined parameter is prevented.
European Patent Application No. 20110195787 (Publication No. EP2610388 A1) relates to a Laundry drying machine comprising a rotatory laundry drum; an electric motor for rotating said rotatory laundry drum about its axis of rotation; hot air generator means configured to supply a drying airflow to the drum during a drying cycle; an electronic control system configured to: provide a signal indicative of the torque that said electric motor provides to the rotatory laundry drum, sense the inside-temperature of the drying airflow inside the drum, sense the output temperature of the airflow which flows out from the rotatory drum, determine a comparison threshold based on the sensed signal, determine a temperature difference between the sensed output temperature and the sensed inside temperature, compare the determined temperature difference with the determined comparison threshold and stop the drying cycle according to the comparison result.
European Patent Application No, 20110195942 (Publication No. 2610401 A1) comprises a rotatory laundry drum designed to rotate about an axis of rotation; an electric motor which is mechanically connected with the rotatory washing drum for rotating said rotatory washing drum about its axis of rotation; hot-air generator means configured to supply a heated airflow to the drum during a drying cycle; and, an electronic control system configured to: provide a sensed signal which is indicative of a torque that said electric motor provides to the rotatory washing drum; determine the value of a parameter that is indicative of the variation of the sensed signal in time, and estimate the laundry load contained within said chamber based on said determined value of said parameter.
European Patent Application No. 20110818424 (Publication No. EP2607546) describes a laundry machine having a drying function and comprises: a rotatory installed drum, a heater that generates hot air, a fan, a filter that filters the hot air, a sensor that senses a hot airflow resistance generated by a flow channel through which the hot air flows, and a controller which determines whether or not the filter is obstructed on the basis of the hot-airflow resistance sensed by the sensor.
European Patent Application No. 20110186051 (Publication No. EP2584086) relates to a clothes drying machine, or to combined clothes washing and drying machine, comprising a drum suitable to receive the clothes to be dried; an air circulating system adapted to circulate a flow of drying air into the drum; an outlet circuit located on the lower portion of the drum, for the exhaust air exiting the drum, a lint filter device arranged in the outlet circuit; a control device for controlling said clothes drying machine during a drying cycle; and, a moisture sensor connected to the control device for measuring the moisture level of the clothes during the drying cycle. The moisture sensor comprises at least two electrical contacts associated to the lint filter device and connected to the control device. The control device is configured for calculating a control parameter indicative of the impedance between the electrical contacts and for controlling the drying cycle according to the value of the control parameter.
Chinese Patent No. CN20020227 (Publication No. CN2479049) describes an automatic device for detecting the drying of clothes of clothes driers, comprising power circuits which provide the current working voltage of the following circuits. The utility model of the automatic device for detecting the drying of clothes is characterized in that the utility model further comprises a temperature and humidity sensing circuit, comprising a driving circuit which receives and amplifies the signals from push buttons and a display circuit, a control circuit of a micro-gyroscope which respectively receives and process the signals from the temperature and humidity sensing circuit and of the driving circuit, a transducer circuit which receives the signals from a control circuit of microcontroller and which generates sounds, and an executing circuit which receives the signals from signals of a control circuit of a microcontroller and which drives high voltage pulses of ignition and from the motor rotation. The utility model reduces the usage cost, is capable of automatically adjust the amount of the heat supply, shortens the clothes drying time, and is capable of automatically discriminate whether or not the clothes are already dry, thereby automatically controlling the clothes drying process.
Chinese Patent No. CN20101104998 (Publication No. CN102140756 A) refers to a method for automatically drying clothes by using a clothes dryer. The method comprises the following steps: sorting a load; heating and drying the load; determining the drying level of the load by combining a system with the temperature and humidity characteristics of the load, and controlling the heating and drying process of the load; and cooling the load. Through this method, the disadvantages of specific procedures in the prior art for drying specific clothes can be overcome, the problem that heavy clothes, such as a bedspread, and the like, cannot be dried automatically are solved, and the function of accurately drying various common clothes by using a common procedure is realized. In addition, the method can realize accurate automatic drying of heavy clothes, such as towel, a bedspread, and the like.
Chinese Patent No. CN2005116061 (Publication No. CN1966841 A) relates to an automatic drying control method, comprising a humidity sensor output value to check the output value variance and determine the minimum output voltage. Broaden the output value and the minimum output voltage, set different dryness degrees as references based on judgment. Compare the voltage value to change Delta V of the current output value with the minimum output voltage with the dryness reference point so as to decide the drying end point. With the output value change as a reference to decide the dryness degree, the convenience of application can be improved. If the voltage change value of the humidity sensor is kept above certain value for a period of time, an over-drying or incomplete drying at the end of the drying process can be prevented. Besides, the inaccurate judgment for the drying end point can be prevented.
According to the above, it can be seen from the state of the art documents that there is a great variety in machines and methods for drying textile clothes, which comprise sensors for sensing the dryness or humidity level of clothes, but this is realized during or at the end of the drying cycle, and it may take a long period of time to sense said condition, which, in some instances, is up to about 20 minutes.
But, what happens when the clothes load already dry before the automatic dryer machine starts the drying cycle? This condition can occur, because housewives or housekeepers in charge of cleaning the garments or linen in general often perform others duties at the same time and forget whether or not they already turned on the drying machine for drying said garments, thus wasting time and power by turning on the machine again, and also overheating the clothes and thereby resulting in an premature deterioration of the clothes.
Consequently, there is a great waste of power that can be prevented if prior to starting the dryer machine the condition of the textile clothes load, whether dry or wet, is sensed.